Method and apparatus for recording and reading out radiation images

ABSTRACT

One surface of a stimulable phosphor sheet supported at a position for image recording is exposed to radiation, and a radiation image is stored on the stimulable phosphor sheet. Image readout is performed from the side of the other surface of the stimulable phosphor sheet supported at the position for image recording. Energy remaining on the stimulable phosphor sheet is then released by irradiating erasing light to an entire area of the stimulable phosphor sheet with a sheet-shaped erasing light source, which has uniform transmissivity to radiation and is located close to the one surface of the stimulable phosphor sheet supported at the position for image recording.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to a radiation image recording andread-out method and apparatus, wherein a radiation image is stored on astimulable phosphor sheet, the stimulable phosphor sheet, on which theradiation image has been stored, is exposed to stimulating rays, whichcause the stimulable phosphor sheet to emit light in proportion to theamount of energy stored thereon during its exposure to radiation, theemitted light is detected, and the radiation image is thereby read outfrom the stimulable phosphor sheet and converted into an electricsignal. This invention particularly relates to an improvement in anerasing light source.

[0003] 2. Description of the Related Art

[0004] It has been proposed to use stimulable phosphors in radiationimage recording and reproducing systems. Specifically, a radiation imageof an object, such as a human body, is recorded on a sheet provided witha layer of the stimulable phosphor (hereinafter referred to as astimulable phosphor sheet). The stimulable phosphor sheet, on which theradiation image has been stored, is then exposed to stimulating rays,such as a laser beam, which cause the stimulable phosphor sheet to emitlight in proportion to the amount of energy stored thereon during itsexposure to the radiation. The light emitted by the stimulable phosphorsheet, upon stimulation thereof, is photoelectrically detected andconverted into an electric image signal. The image signal is thenprocessed and used for the reproduction of the radiation image of theobject as a visible image on a recording material. The radiation imagerecording and reproducing systems described above are referred to ascomputed radiography (CR).

[0005] The applicant proposed built-in types of radiation imagerecording and read-out apparatuses, comprising: (i) circulation andconveyance means for conveying at least one stimulable phosphor sheetalong a circulation path, (ii) an image recording section, which islocated in the circulation path and in which a radiation image of anobject is stored on the stimulable phosphor sheet, (iii) an imageread-out section, which is located in the circulation path and in whichthe radiation image is read out from the stimulable phosphor sheet, and(iv) an erasing section, which is located in the circulation path and inwhich energy remaining on the stimulable phosphor sheet after theradiation image has been read out therefrom is released. The built-intypes of radiation image recording and read-out apparatuses aredisclosed in, for example, U.S. Pat. Nos. 4,543,479 and 4,851,679, andJapanese Unexamined Patent Publication No. 3(1991)-238441. With theproposed built-in types of radiation image recording and read-outapparatuses, the stimulable phosphor sheet is utilized repeatedly and isprocessed efficiently.

[0006] As for the radiation image recording and read-out apparatusesdescribed above, from the point of view of keeping the emitted lightdetection time short, reducing the size of the apparatus, and keepingthe cost low, it has been proposed to utilize a line sensor comprising acharge coupled device (CCD) image sensor, or the like, as photoelectricread-out means. The utilization of the line sensor as the photoelectricread-out means is disclosed in, for example, Japanese Unexamined PatentPublication Nos. 60(1985)-111568, 60(1985)-236354, and 1(1989)-101540.

[0007] Basically, the radiation image recording and read-out apparatusesof such types comprise:

[0008] i) a read-out unit comprising (a) stimulating ray irradiatingmeans for linearly irradiating stimulating rays onto an area of astimulable phosphor sheet, on which a radiation image has been stored,the stimulating rays causing the stimulable phosphor sheet to emit lightin proportion to an amount of energy stored thereon during its exposureto radiation, and (b) a line sensor, which comprises a plurality ofphotoelectric conversion devices arrayed along the linear area of thestimulable phosphor sheet exposed to the linear stimulating rays, and

[0009] ii) sub-scanning means for moving the stimulable phosphor sheetwith respect to the read-out unit and in a direction (a sub-scanningdirection), which is approximately normal to a length direction of thelinear area of the stimulable phosphor sheet exposed to the linearstimulating rays (a main scanning direction).

[0010] In particular, in cases where the radiation image recording andread-out apparatuses are constituted such that the stimulable phosphorsheet is kept stationary, and the read-out unit is moved in thesub-scanning direction, the sizes of the radiation image recording andread-out apparatuses as a whole are capable of being kept small. As anexample of the radiation image recording and read-out apparatus havingthe constitution described above, in order for energy, which remains onthe stimulable phosphor sheet after the radiation image has been readout from the stimulable phosphor sheet, to be released, there hasheretofore been proposed a radiation image recording and read-outapparatus, wherein an erasing light source is located on the sidebackward from the read-out unit, and erasing light is irradiatedsimultaneously to the entire surface of the stimulable phosphor sheet.As a different example of the radiation image recording and read-outapparatus having the constitution described above, in order for energy,which remains on the stimulable phosphor sheet after the radiation imagehas been read out from the stimulable phosphor sheet, to be released,there has heretofore been proposed a radiation image recording andread-out apparatus, wherein an erasing light source is located withinthe read-out unit, and the read-out unit is moved in order to irradiateerasing light successively to the entire surface of the stimulablephosphor sheet. The examples of the radiation image recording andread-out apparatuses described above are proposed in, for example,Japanese Unexamined Patent Publication No. 63(1988)-189855.

[0011] However, with the proposed radiation image recording and read-outapparatus, wherein the erasing light source is located on the sidebackward from the read-out unit, and the erasing light is irradiatedsimultaneously to the entire surface of the stimulable phosphor sheet inorder to release energy remaining on the stimulable phosphor sheet, theread-out unit located between the stimulable phosphor sheet and theerasing light source intercepts the erasing light. Therefore, theproblems occur in that the erasing light cannot be uniformly irradiatedto the enter surface of the stimulable phosphor sheet.

[0012] With the proposed radiation image recording and read-outapparatus, wherein the erasing light source is located within theread-out unit, and the read-out unit is moved in order to irradiate theerasing light successively to the entire surface of the stimulablephosphor sheet, both the image read-out means and the erasing lightsource are accommodated within the read-out unit. Therefore, theproblems occur in that the constitution of the read-out unit cannot bekept simple, and the size of the read-out unit cannot be kept small.

SUMMARY OF THE INVENTION

[0013] The primary object of the present invention is to provide aradiation image recording and read-out method, which is capable of beingperformed with an apparatus having a small size as a whole, and in whichan erasing light source need not be moved.

[0014] Another object of the present invention is to provide anapparatus for carrying out the radiation image recording and read-outmethod.

[0015] The present invention provides a radiation image recording andread-out method, comprising the steps of:

[0016] i) supporting a stimulable phosphor sheet at a position for imagerecording, at which one surface of the stimulable phosphor sheet isexposed to radiation,

[0017] ii) exposing the one surface of the stimulable phosphor sheet,which is supported at the position for image recording, to theradiation, a radiation image being thereby stored on the stimulablephosphor sheet,

[0018] iii) performing an image read-out operation from a side of theother surface of the stimulable phosphor sheet supported at the positionfor image recording, which other surface is opposite to the one surfaceof the stimulable phosphor sheet exposed to the radiation, the imageread-out operation being performed by irradiating stimulating rays intwo-dimensional directions to the stimulable phosphor sheet, on whichthe radiation image has been stored during its exposure to theradiation, the stimulating rays causing the stimulable phosphor sheet toemit light in proportion to an amount of energy stored thereon duringits exposure to the radiation, and photoelectrically detecting theemitted light, an image signal, which represents the radiation imagehaving been stored on the stimulable phosphor sheet, being therebyobtained, and

[0019] iv) releasing energy, which remains on the stimulable phosphorsheet after the image signal has been obtained from the stimulablephosphor sheet, by irradiating erasing light to an entire area of thestimulable phosphor sheet with a sheet-shaped erasing light source, thesheet-shaped erasing light source being located in close vicinity to thestimulable phosphor sheet and on a side of the one surface of thestimulable phosphor sheet supported at the position for image recording,which one surface is exposed to the radiation, the sheet-shaped erasinglight source having uniform transmissivity to the radiation.

[0020] The irradiation of the stimulating rays in two-dimensionaldirections to the stimulable phosphor sheet, on which the radiationimage has been stored, may be performed in one of various ways. Forexample, one light beam of the stimulating rays may be deflected in themain scanning direction and the sub-scanning direction, and thestimulable phosphor sheet may be scanned with the light spot of thelight beam in two-dimensional directions. Alternatively, one light beamof the stimulating rays may be deflected in the main scanning directionalone and may be moved with respect to the stimulable phosphor sheet inthe sub-scanning direction. As another alternative, the stimulating raysmay be irradiated linearly to an area on the stimulable phosphor sheetalong the main scanning direction, the linear stimulating rays may bemoved in the sub-scanning direction, and the stimulable phosphor sheetmay thereby be scanned with the stimulating rays in two-dimensionaldirections. As a further alternative, the stimulating rays may beirradiated simultaneously to the entire area of the stimulable phosphorsheet.

[0021] The term “sheet-shaped erasing light source having uniformtransmissivity to radiation” as used herein means that the sheet-shapederasing light source is substantially free from a structure, which isdiscontinuous with respect to the transmissivity to the radiation.Specifically, the sheet-shaped erasing light source has uniformtransmissivity to the radiation such that, when the radiation carryingimage information passes through the sheet-shaped erasing light source,the structure of the sheet-shaped erasing light source is not recordedas a gray level image pattern on the stimulable phosphor sheet, and suchthat the sheet-shaped erasing light source is capable of transmittingthe radiation sufficiently for the image information carried by theradiation to be stored on the stimulable phosphor sheet. Thetransmissivity of the sheet-shaped erasing light source with respect tothe radiation should preferably be as high as possible.

[0022] In the radiation image recording and read-out method inaccordance with the present invention, the sheet-shaped erasing lightsource may comprise an organic electroluminescence device.Alternatively, the sheet-shaped erasing light source may comprise atransparent sheet, which has light diffusing properties, the transparentsheet being capable of radiating out the erasing light from a surface,which stands facing the stimulable phosphor sheet, toward the stimulablephosphor sheet, and

[0023] light sources, each of which is located at one of two ends of thetransparent sheet and produces the erasing light such that the erasinglight enters from the one end of the transparent sheet into thetransparent sheet.

[0024] In order for the transparent sheet to be imparted with the lightdiffusing properties, at least either one of two surfaces of thetransparent sheet may be formed as a light diffusing surface.Alternatively, the transparent sheet may contain light diffusingparticles dispersed therein.

[0025] Also, the radiation image recording and read-out method inaccordance with the present invention may be modified such that thestimulable phosphor sheet comprises a sheet-shaped transparent substrateand a stimulable phosphor layer overlaid on the sheet-shaped transparentsubstrate, and

[0026] the transparent sheet of the sheet-shaped erasing light sourceacts also as the sheet-shaped transparent substrate of the stimulablephosphor sheet.

[0027] Further, in the radiation image recording and read-out method inaccordance with the present invention, the stimulable phosphor sheet maybe kept stationary at the position for image recording, and the imageread-out operation (i.e., the irradiation of the stimulating rays to thestimulable phosphor sheet and the detection of the light emitted by thestimulable phosphor sheet) may thereby be performed. Alternatively,after the radiation image has been recorded on the stimulable phosphorsheet, the stimulable phosphor sheet, on which the radiation image hasbeen stored, may be conveyed by conveyance means to an image read-outsection, and the image read-out operation may be performed in the imageread-out section. In particular, the radiation image recording andread-out method in accordance with the present invention shouldpreferably be modified such that the stimulable phosphor sheet is keptstationary at the position for image recording, and

[0028] the image read-out operation is performed with a read-out unitfor irradiating the stimulating rays to the stimulable phosphor sheet ina one-dimensional direction along a main scanning direction anddetecting the light, which is emitted by the stimulable phosphor sheetwhen the stimulating rays are irradiated to the stimulable phosphorsheet in the one-dimensional direction, the read-out unit being moved ina sub-scanning direction.

[0029] The sub-scanning direction is the direction intersecting with themain scanning direction. In cases where the read-out unit irradiates thestimulating rays to the stimulable phosphor sheet in the one-dimensionaldirection along the main scanning direction and is moved in thesub-scanning direction, the stimulating rays are irradiated to thestimulable phosphor sheet in two-dimensional directions. Ordinarily, thesub-scanning direction is normal to the main scanning direction.

[0030] The read-out unit should preferably comprise a linear stimulatingray source, which linearly irradiates the stimulating rays to an area ofthe stimulable phosphor sheet, and

[0031] a line sensor, which is located along the linear area of thestimulable phosphor sheet exposed to the linear stimulating rays andphotoelectrically detects the light emitted by the stimulable phosphorsheet when the stimulating rays are irradiated to the stimulablephosphor sheet.

[0032] The present invention also provides an apparatus for carrying outthe radiation image recording and read-out method in accordance with thepresent invention. Specifically, the present invention also provides aradiation image recording and read-out apparatus, comprising:

[0033] i) an image recording section for supporting a stimulablephosphor sheet at a position for image recording, at which one surfaceof the stimulable phosphor sheet is exposed to radiation,

[0034] ii) image read-out means located on a side of the other surfaceof the stimulable phosphor sheet supported at the position for imagerecording, which other surface is opposite to the one surface of thestimulable phosphor sheet exposed to the radiation, the image read-outmeans performing an image read-out operation by irradiating stimulatingrays in two-dimensional directions to the stimulable phosphor sheet, onwhich a radiation image has been stored during its exposure to theradiation, the stimulating rays causing the stimulable phosphor sheet toemit light in proportion to an amount of energy stored thereon duringits exposure to the radiation, and photoelectrically detecting theemitted light, an image signal, which represents the radiation imagehaving been stored on the stimulable phosphor sheet, being therebyobtained, and

[0035] iii) a sheet-shaped erasing light source located in closevicinity to the stimulable phosphor sheet and on a side of the onesurface of the stimulable phosphor sheet supported at the position forimage recording, which one surface is exposed to the radiation, thesheet-shaped erasing light source having uniform transmissivity to theradiation, the sheet-shaped erasing light source releasing energy, whichremains on the stimulable phosphor sheet after the image signal has beenobtained from the stimulable phosphor sheet, by irradiating erasinglight to an entire area of the stimulable phosphor sheet.

[0036] In the radiation image recording and read-out apparatus inaccordance with the present invention, the sheet-shaped erasing lightsource may comprise an organic electroluminescence device.Alternatively, the sheet-shaped erasing light source may comprise atransparent sheet, which has light diffusing properties, the transparentsheet being capable of radiating out the erasing light from a surface,which stands facing the stimulable phosphor sheet, toward the stimulablephosphor sheet, and

[0037] light sources, each of which is located at one of two ends of thetransparent sheet and produces the erasing light such that the erasinglight enters from the one end of the transparent sheet into thetransparent sheet.

[0038] In order for the transparent sheet to be imparted with the lightdiffusing properties, at least either one of two surfaces of thetransparent sheet may be formed as a light diffusing surface.Alternatively, the transparent sheet may contain light diffusingparticles dispersed therein.

[0039] Also, the radiation image recording and read-out apparatus inaccordance with the present invention may be modified such that thestimulable phosphor sheet comprises a sheet-shaped transparent substrateand a stimulable phosphor layer overlaid on the sheet-shaped transparentsubstrate, and

[0040] the transparent sheet of the sheet-shaped erasing light sourceacts also as the sheet-shaped transparent substrate of the stimulablephosphor sheet.

[0041] Further, in the radiation image recording and read-out apparatusin accordance with the present invention, the stimulable phosphor sheetmay be kept stationary at the position for image recording, and theimage read-out operation (i.e., the irradiation of the stimulating raysto the stimulable phosphor sheet and the detection of the light emittedby the stimulable phosphor sheet) may thereby be performed.Alternatively, after the radiation image has been recorded on thestimulable phosphor sheet, the stimulable phosphor sheet, on which theradiation image has been stored, may be conveyed by conveyance means toan image read-out section, and the image read-out operation may beperformed in the image read-out section. In particular, the radiationimage recording and read-out apparatus in accordance with the presentinvention should preferably be modified such that the stimulablephosphor sheet is kept stationary at the position for image recording,and

[0042] the image read-out means comprises:

[0043] a) a read-out unit for irradiating the stimulating rays to thestimulable phosphor sheet in a one-dimensional direction along a mainscanning direction and detecting the light, which is emitted by thestimulable phosphor sheet when the stimulating rays are irradiated tothe stimulable phosphor sheet in the one-dimensional direction, and

[0044] b) unit moving means for moving the read-out unit in asub-scanning direction.

[0045] In such cases, the read-out unit should preferably comprise alinear stimulating ray source, which linearly irradiates the stimulatingrays to an area of the stimulable phosphor sheet, and

[0046] a line sensor, which is located along the linear area of thestimulable phosphor sheet exposed to the linear stimulating rays andphotoelectrically detects the light emitted by the stimulable phosphorsheet when the stimulating rays are irradiated to the stimulablephosphor sheet.

[0047] With the radiation image recording and read-out method andapparatus in accordance with the present invention, as the erasing lightsource for releasing energy, which remains on the stimulable phosphorsheet after the image signal has been obtained from the stimulablephosphor sheet, the sheet-shaped erasing light source is employed. Thesheet-shaped erasing light source is located in close vicinity to thestimulable phosphor sheet and on the side of the one surface of thestimulable phosphor sheet supported at the position for image recording,which one surface is exposed to the radiation. Also, the sheet-shapederasing light source has uniform transmissivity to the radiation. Sincethe erasing light source has the sheet-like shape, a large space is notrequired for installing the erasing light source. Also, a mechanism formoving the erasing light source need not be provided. Therefore, thesize of the radiation image recording and read-out apparatus as a wholeis capable of being kept small, and the structure of the radiation imagerecording and read-out apparatus is capable of being kept simple.

[0048] Also, with the radiation image recording and read-out method andapparatus in accordance with the present invention, the stimulablephosphor sheet may be kept stationary at the position for imagerecording, and the image read-out operation may be performed with theimage read-out means comprising (a) the read-out unit for irradiatingthe stimulating rays to the stimulable phosphor sheet in aone-dimensional direction along the main scanning direction anddetecting the light, which is emitted by the stimulable phosphor sheetwhen the stimulating rays are irradiated to the stimulable phosphorsheet in the one-dimensional direction, and (b) the unit moving meansfor moving the read-out unit in the sub-scanning direction. In suchcases, a space for the conveyance of the stimulable phosphor sheet andconveyance means are not necessary. Therefore, the size of the radiationimage recording and read-out apparatus as a whole is capable of beingminimized.

[0049] Further, the read-out unit may comprise the linear stimulatingray source, which linearly irradiates the stimulating rays to the areaof the stimulable phosphor sheet, and the line sensor, which is locatedalong the linear area of the stimulable phosphor sheet exposed to thelinear stimulating rays and photoelectrically detects the light emittedby the stimulable phosphor sheet when the stimulating rays areirradiated to the stimulable phosphor sheet. The linear stimulating raysource is capable of being formed to a size smaller than a pointscanning type of light source, with which one light beam is deflectedand caused to scan on the stimulable phosphor sheet. Also, the linesensor is smaller than a photomultiplier, or the like. Therefore, insuch cases, the size of the readout unit as a whole is capable of beingset to be small, and the size of the radiation image recording andread-out apparatus as a whole is consequently capable of being set to besmall.

BRIEF DESCRIPTION OF THE DRAWINGS

[0050]FIG. 1 is a schematic side view showing an embodiment of theradiation image recording and read-out apparatus in accordance with thepresent invention,

[0051]FIG. 2 is a front view showing a line light source employed in theembodiment of FIG. 1,

[0052]FIG. 3 is a plan view showing a line sensor employed in theembodiment of FIG. 1,

[0053]FIG. 4 is a front view showing a light collecting lens arrayemployed in the embodiment of FIG. 1,

[0054]FIG. 5 is a perspective view showing a different example of anerasing light source employed in the radiation image recording andread-out apparatus in accordance with the present invention, and

[0055]FIG. 6 is a perspective view showing a further different exampleof an erasing light source employed in the radiation image recording andread-out apparatus in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0056] The present invention will hereinbelow be described in furtherdetail with reference to the accompanying drawings.

[0057]FIG. 1 is a schematic side view showing an embodiment of theradiation image recording and read-out apparatus in accordance with thepresent invention. As illustrated in FIG. 1, the radiation imagerecording and read-out apparatus comprises a radiation image recordingsection 10 and a radiation image read-out section 20.

[0058] The radiation image recording section 10 is provided with anobject support base 12 for supporting an object 11, such as a humanbody, at a predetermined position. A grid 16 for removing scatteredradiation is located on the side rearward from the object support base12. Also, a stimulable phosphor sheet 2 is supported at a predeterminedposition for image recording and on the side rearward from the grid 16.The stimulable phosphor sheet 2 comprises a transparent substrate 2A anda stimulable phosphor layer 2B overlaid on the transparent substrate 2A.The object support base 12 has transmissivity to radiation. Asheet-shaped erasing light source 40 is located on the side of onesurface of the stimulable phosphor sheet 2, which one surface is exposedto radiation 13, such that the sheet-shaped erasing light source 40 isin close contact with the stimulable phosphor sheet 2.

[0059] In the radiation image read-out section 20, a radiation image isread out with a read-out unit 21 from the stimulable phosphor sheet 2,on which the radiation image has been stored. The read-out unit 21comprises a line light source (linear stimulating ray source) 22, a CCDline sensor 23, and a light collecting lens array 25, which is locatedon the side forward from the CCD line sensor 23 so as to stand facingthe stimulable phosphor sheet 2. The read-out unit 21 is provided with afemale thread region (not shown) for engagement with a ball screw 14,which extends vertically and is rotated by movement means 15. When theball screw 14 is rotated forwardly and reversely, the read-out unit 21is moved upwardly and downwardly by the ball screw 14.

[0060]FIG. 2 is a front view showing the line light source 22. Asillustrated in FIG. 2, the line light source 22 comprises a laser diodearray 33 and a cylindrical lens 34. The laser diode array 33 comprises aplurality of laser diodes 33 a, 33 b, 33 c, . . . arrayed in a line. Byway of example, each of the laser diodes 33 a, 33 b, 33 c, . . .produces a laser beam (the stimulating rays) having wavelengths fallingwithin the range of 650 nm to 690 nm. The laser diodes 33 a, 33 b, 33 c,. . . respectively produce stimulating rays 31 a, 31 b, 31 c, . . . in adivergent light state. The stimulating rays 31 a, 31 b, 31 c, . . . ,which have been produced by the laser diodes 33 a, 33 b, 33 c, . . . ,are converged by the cylindrical lens 34 with respect to only onedirection (only in the plane of the sheet of FIG. 1) and into fan beams.The stimulating rays 31, which are composed of the fan beams standing ina row, are linearly irradiated onto the linear area of the stimulablephosphor sheet 2.

[0061]FIG. 3 is a plan view showing the CCD line sensor 23. Asillustrated in FIG. 3, the CCD line sensor 23 comprises a plurality ofsensor chips (photoelectric conversion devices) 23 a, 23 a, . . . ,which are arrayed in a line. In this embodiment, a light receiving widthof the CCD line sensor 23, which light receiving width is taken in thedirection normal to the array direction of the sensor chips 23 a, 23 a,. . . , i.e. a width W of each of the sensor chips 23 a, 23 a, . . . ,is approximately equal to 100 μM.

[0062] The CCD line sensor 23 is located in an orientation such that thesensor chips 23 a, 23 a, . . . stand side by side along a lengthdirection of the linear area of the stimulable phosphor sheet 2 exposedto the linear stimulating rays 31 in FIG. 1 (i.e., along the mainscanning direction indicated by the arrow X in FIG. 1). In cases wherethe stimulable phosphor sheet 2 has a large width, the CCD line sensor23 may be composed of a plurality of line sensors, which are arrayed soas to stand in a row along the length direction of the CCD line sensor23.

[0063]FIG. 4 is a front view showing the light collecting lens array 25,which is located on the side forward from the CCD line sensor 23. Asillustrated in FIG. 4, the light collecting lens array 25 comprises, forexample, a plurality of distributed index lenses 25 a, 25 b, 25 c, 25 d,. . . , which are arrayed in a line. The light collecting lens array 25is located in an orientation such that the distributed index lenses 25a, 25 b, 25 c, 25 d, . . . , stand side by side along the lengthdirection of the linear area of the stimulable phosphor sheet 2 exposedto the linear stimulating rays 31, i.e. along the main scanningdirection indicated by the arrow X in FIG. 1. Each of the distributedindex lenses 25 a, 25 b, 25 c, 25 d, . . . collects light 35, which isemitted by the stimulable phosphor sheet 2. Also, as illustrated in FIG.1, each of the distributed index lenses 25 a, 25 b, 25 c, 25 d, . . .guides the emitted light 35 toward the CCD line sensor 23.

[0064] Though not shown, a filter for filtering out the stimulating rays31, which have been reflected from the stimulable phosphor sheet 2, islocated between the CCD line sensor 23 and the light collecting lensarray 25.

[0065] The sheet-shaped erasing light source 40 produces the erasinglight, which has wavelengths falling within a stimulation wavelengthregion for the stimulable phosphor sheet 2. The sheet-shaped erasinglight source 40 has uniform transmissivity to the radiation 13. Also,the sheet-shaped erasing light source 40 has a size at least identicalwith the size of the stimulable phosphor sheet 2 and irradiates theerasing light simultaneously to the entire area of the stimulablephosphor sheet 2. After the radiation image has been read out from thestimulable phosphor sheet 2, the erasing light is irradiated to thestimulable phosphor sheet 2, and energy remaining on the stimulablephosphor sheet 2 is thereby released from the stimulable phosphor sheet2.

[0066] Specifically, the sheet-shaped erasing light source 40 comprisesan organic electroluminescence device. The sheet-shaped erasing lightsource 40 has a sufficient transmissivity to the radiation 13 and issubstantially free from a structure, which is discontinuous with respectto the transmissivity to the radiation 13. Therefore, when the radiation13 passes through the sheet-shaped erasing light source 40 and isirradiated to the stimulable phosphor sheet 2, and the radiation imageof the object 11 is thereby recorded on the stimulable phosphor sheet 2,no image pattern of the sheet-shaped erasing light source 40 issimultaneously recorded on the stimulable phosphor sheet 2.

[0067] In the radiation image recording and read-out apparatus inaccordance with the present invention, in lieu of the sheet-shapederasing light source 40, a sheet-shaped erasing light source 40∝ shownin FIG. 5 or a sheet-shaped erasing light source 40′ shown in FIG. 6 maybe employed.

[0068] The sheet-shaped erasing light source 40′ shown in FIG. 5comprises a transparent sheet 41, which may be made from an acrylicresin, or the like. The sheet-shaped erasing light source 40′ alsocomprises aperture types of fluorescent lamps 42, 42, each of which islocated at one of two ends 41 a, 41 a of the transparent sheet 41. Eachof the fluorescent lamps 42, 42 has an aperture 43. The aperture 43 ofeach of the fluorescent lamps 42, 42 is in contact with thecorresponding end 41 a of the transparent sheet 41. The erasing lightenters from the apertures 43, 43 of the fluorescent lamps 42, 42 intothe transparent sheet 41. A radiation incidence surface 41 b of thetransparent sheet 41 is formed as a light diffusing surface. The lightdiffusing surface acts such that the erasing light is efficientlyradiated out from a surface 41 c, which stands facing the stimulablephosphor sheet 2. However, it is sufficient for the transparent sheet 41to have light diffusing properties and to be capable of radiating outthe erasing light from the surface 41 c, which stands facing thestimulable phosphor sheet 2. Therefore, the radiation incidence surface41 b of the transparent sheet 41 need not necessarily be formed as thelight diffusing surface. For example, instead of the radiation incidencesurface 41 b of the transparent sheet 41 being formed as the lightdiffusing surface, the surface 41 c, which stands facing the stimulablephosphor sheet 2, may be formed as the light diffusing surface. Asanother alternative, the transparent sheet 41 may contain lightdiffusing particles dispersed in the transparent sheet 41. In lieu ofthe aperture types of the fluorescent lamps 42, 42, cold cathodefluorescent lamps, and the like, may be employed.

[0069] Also, as illustrated in FIG. 6, the stimulable phosphor layer 2Bmay be overlaid on the transparent sheet 41 of the sheet-shaped erasinglight source 40′, and the transparent sheet 41 may acts also as thetransparent substrate 2A of the stimulable phosphor sheet 2.Specifically, in the example of FIG. 6, the sheet-shaped erasing lightsource 40 and the stimulable phosphor sheet 2 are combined into anintegral body.

[0070] How the aforesaid embodiment of the radiation image read-outapparatus in accordance with the present invention operates will bedescribed hereinbelow.

[0071] When an operation for recording the radiation image of the object11 on the stimulable phosphor sheet 2 is to be performed, the object 11lies at the aforesaid predetermined position on the object support base12. The radiation 13, such as X-rays, is then produced by a radiationsource (not shown) and irradiated to the object 11. The radiation 13carrying image information of the object 11 impinges upon the stimulablephosphor sheet 2. In this manner, the radiation image of the object 11is recorded (i.e., stored) on the stimulable phosphor sheet 2.

[0072] At the time at which the image recording operation for recordingthe radiation image of the object 11 on the stimulable phosphor sheet 2is performed, the read-out unit 21 is set at the waiting positionindicated by the broken lines in FIG. 1. When the image recordingoperation has been finished, the read-out unit 21 is moved upwardly at apredetermined speed. At this time, the laser diode array 33 of the linelight source 22 is activated to produce the stimulating rays 31, and thefan beam-like stimulating rays 31 are linearly irradiated to the lineararea of the stimulable phosphor sheet 2, which linear area extends inthe main scanning direction indicated by the arrow X. Also, the read-outunit 21 is moved in the sub-scanning direction indicated by the arrow Y,which sub-scanning direction is normal to the main scanning directionindicated by the arrow X. As a result, the stimulable phosphor sheet 2is scanned with the stimulating rays 31 in two-dimensional directions.

[0073] When the stimulating rays 31 are linearly irradiated to the areaof the stimulable phosphor sheet 2, the linear area of the stimulablephosphor sheet 2 exposed to the linear stimulating rays 31 emits thelight 35 having intensity in accordance with the radiation image havingbeen stored on the stimulable phosphor sheet 2. The emitted light 35 iscollected by the light collecting lens array 25, impinges upon the CCDline sensor 23, and is received by the CCD line sensor 23.

[0074] The CCD line sensor 23 photoelectrically detects the emittedlight 35 and feeds out a light detection signal. The light detectionsignal is fed into a read-out circuit (not shown) and subjected toamplification and analog-to-digital conversion. A read-out image signalS, which has thus been obtained, is fed out from the radiation imagerecording and read-out apparatus. When necessary, the read-out imagesignal S is subjected to processing, such as gradation processing andprocessing in the frequency domain. The read-out image signal S is thenfed into image displaying means, such as a CRT display device, or animage recording apparatus, such as a light scanning recording apparatus,and is utilized for reproducing the image represented by the read-outimage signal S, i.e. the radiation image having been stored on thestimulable phosphor sheet 2.

[0075] When the read-out unit 21 is moved to a sub-scanning end positionand the image read-out operation is finished, the read-out unit 21 ismoved downwardly toward the waiting position described above.

[0076] Thereafter, the sheet-shaped erasing light source 40 is activatedto produce the erasing light. The erasing light, which has been producedby the sheet-shaped erasing light source 40, is irradiated uniformly tothe entire area of the stimulable phosphor sheet 2. When the stimulablephosphor sheet 2 is exposed to the erasing light having wavelengthsfalling within the stimulation wavelength region for the stimulablephosphor sheet 2, energy remaining on the stimulable phosphor layer 2Bof the stimulable phosphor sheet 2 is released. Therefore, thestimulable phosphor sheet 2 is capable of being again utilized for therecording of a radiation image.

[0077] After the read-out unit 21 has been returned to the waitingposition described above, the radiation 13 carrying the imageinformation of the object 11 may be irradiated to the stimulablephosphor sheet 2. In this manner, the radiation image of the object 11is capable of being stored on the stimulable phosphor sheet 2.

[0078] As described above, with the aforesaid embodiment of theradiation image recording and read-out apparatus in accordance with thepresent invention, the erasing light source 40 has the sheet-like shapeand is located on the side of the one surface of the stimulable phosphorsheet 2, which one surface is exposed to the radiation 13, such that thesheet-shaped erasing light source 40 is in close contact with thestimulable phosphor sheet 2. Therefore, the sheet-shaped erasing lightsource 40 is thin and has a small size, and a space for movement of theerasing light is not necessary. Accordingly, the size of the radiationimage recording and read-out apparatus as a whole is capable of beingkept small.

[0079] In lieu of the laser diode array 33, the line light source 22 maycomprise a light emitting diode (LED) array.

[0080] In the embodiment described above, the stimulable phosphor sheet2 is kept stationary at the position for image recording, and theradiation image is read out from the stimulable phosphor sheet 2 whilethe stimulable phosphor sheet 2 is being kept in this state.Alternatively, after the radiation image has been recorded on thestimulable phosphor sheet 2 at the position for image recording, thestimulable phosphor sheet 2 may be moved to a predetermined position forimage readout, and the radiation image may be read out from thestimulable phosphor sheet 2 at the position for image readout.

[0081] Also, in the embodiment described above, the radiation imageread-out section 20 is provided with the read-out unit 21, whichcomprises the line light source 22 and the CCD line sensor 23.Alternatively, a read-out unit may be employed, which comprises pointscanning means and photoelectric conversion means constituted of aphotomultiplier sensor.

[0082] In the aforesaid embodiment of the radiation image read-outapparatus in accordance with the present invention, the stimulablephosphor sheet for storing the radiation image may be an ordinarystimulable phosphor sheet having both the functions for absorbingradiation and the functions for storing energy from the radiation.Alternatively, the stimulable phosphor sheet may be a stimulablephosphor sheet proposed in, for example, Japanese Patent Application No.11(1999)-372978. Such that the functions for absorbing radiation and thefunctions for storing energy from the radiation may be separated fromeach other, the proposed stimulable phosphor sheet contains a layer of aphosphor for radiation absorption, which is capable of absorbingradiation and being caused to emit light having wavelengths fallingwithin an ultraviolet to visible region, and a layer of a stimulablephosphor for energy storage, which is capable of absorbing light havingwavelengths falling within the ultraviolet to visible region and therebystoring energy of the light having wavelengths falling within theultraviolet to visible region, and which is capable of being stimulatedby light having wavelengths falling within a visible to infrared regionand thereby radiating out the stored energy as emitted light. As anotheralternative, the stimulable phosphor sheet may be one of various otherkinds of stimulable phosphor sheets.

What is claimed is:
 1. A radiation image recording and read-out method,comprising the steps of: i) supporting a stimulable phosphor sheet at aposition for image recording, at which one surface of the stimulablephosphor sheet is exposed to radiation, ii) exposing the one surface ofthe stimulable phosphor sheet, which is supported at the position forimage recording, to the radiation, a radiation image being therebystored on the stimulable phosphor sheet, iii) performing an imageread-out operation from a side of the other surface of the stimulablephosphor sheet supported at the position for image recording, whichother surface is opposite to the one surface of the stimulable phosphorsheet exposed to the radiation, the image read-out operation beingperformed by irradiating stimulating rays in two-dimensional directionsto the stimulable phosphor sheet, on which the radiation image has beenstored during its exposure to the radiation, the stimulating rayscausing the stimulable phosphor sheet to emit light in proportion to anamount of energy stored thereon during its exposure to the radiation,and photoelectrically detecting the emitted light, an image signal,which represents the radiation image having been stored on thestimulable phosphor sheet, being thereby obtained, and iv) releasingenergy, which remains on the stimulable phosphor sheet after the imagesignal has been obtained from the stimulable phosphor sheet, byirradiating erasing light to an entire area of the stimulable phosphorsheet with a sheet-shaped erasing light source, the sheet-shaped erasinglight source being located in close vicinity to the stimulable phosphorsheet and on a side of the one surface of the stimulable phosphor sheetsupported at the position for image recording, which one surface isexposed to the radiation, the sheet-shaped erasing light source havinguniform transmissivity to the radiation.
 2. A method as defined in claim1 wherein the sheet-shaped erasing light source comprises an organicelectroluminescence device.
 3. A method as defined in claim 1 whereinthe sheet-shaped erasing light source comprises a transparent sheet,which has light diffusing properties, the transparent sheet beingcapable of radiating out the erasing light from a surface, which standsfacing the stimulable phosphor sheet, toward the stimulable phosphorsheet, and light sources, each of which is located at one of two ends ofthe transparent sheet and produces the erasing light such that theerasing light enters from the one end of the transparent sheet into thetransparent sheet.
 4. A method as defined in claim 3 wherein at leasteither one of two surfaces of the transparent sheet is formed as a lightdiffusing surface.
 5. A method as defined in claim 3 wherein thetransparent sheet contains light diffusing particles dispersed therein.6. A method as defined in claim 3, 4, or 5 wherein the stimulablephosphor sheet comprises a sheet-shaped transparent substrate and astimulable phosphor layer overlaid on the sheet-shaped transparentsubstrate, and the transparent sheet of the sheet-shaped erasing lightsource acts also as the sheet-shaped transparent substrate of thestimulable phosphor sheet.
 7. A method as defined in claim 1, 2, 3, 4,or 5 wherein the stimulable phosphor sheet is kept stationary at theposition for image recording, and the image read-out operation isperformed with a read-out unit for irradiating the stimulating rays tothe stimulable phosphor sheet in a one-dimensional direction along amain scanning direction and detecting the light, which is emitted by thestimulable phosphor sheet when the stimulating rays are irradiated tothe stimulable phosphor sheet in the one-dimensional direction, theread-out unit being moved in a sub-scanning direction.
 8. A method asdefined in claim 7 wherein the read-out unit comprises a linearstimulating ray source, which linearly irradiates the stimulating raysto an area of the stimulable phosphor sheet, and a line sensor, which islocated along the linear area of the stimulable phosphor sheet exposedto the linear stimulating rays and photoelectrically detects the lightemitted by the stimulable phosphor sheet when the stimulating rays areirradiated to the stimulable phosphor sheet.
 9. A radiation imagerecording and read-out apparatus, comprising: i) an image recordingsection for supporting a stimulable phosphor sheet at a position forimage recording, at which one surface of the stimulable phosphor sheetis exposed to radiation, ii) image read-out means located on a side ofthe other surface of the stimulable phosphor sheet supported at theposition for image recording, which other surface is opposite to the onesurface of the stimulable phosphor sheet exposed to the radiation, theimage read-out means performing an image read-out operation byirradiating stimulating rays in two-dimensional directions to thestimulable phosphor sheet, on which a radiation image has been storedduring its exposure to the radiation, the stimulating rays causing thestimulable phosphor sheet to emit light in proportion to an amount ofenergy stored thereon during its exposure to the radiation, andphotoelectrically detecting the emitted light, an image signal, whichrepresents the radiation image having been stored on the stimulablephosphor sheet, being thereby obtained, and iii) a sheet-shaped erasinglight source located in close vicinity to the stimulable phosphor sheetand on a side of the one surface of the stimulable phosphor sheetsupported at the position for image recording, which one surface isexposed to the radiation, the sheet-shaped erasing light source havinguniform transmissivity to the radiation, the sheet-shaped erasing lightsource releasing energy, which remains on the stimulable phosphor sheetafter the image signal has been obtained from the stimulable phosphorsheet, by irradiating erasing light to an entire area of the stimulablephosphor sheet.
 10. An apparatus as defined in claim 9 wherein thesheet-shaped erasing light source comprises an organicelectroluminescence device.
 11. An apparatus as defined in claim 9wherein the sheet-shaped erasing light source comprises a transparentsheet, which has light diffusing properties, the transparent sheet beingcapable of radiating out the erasing light from a surface, which standsfacing the stimulable phosphor sheet, toward the stimulable phosphorsheet, and light sources, each of which is located at one of two ends ofthe transparent sheet and produces the erasing light such that theerasing light enters from the one end of the transparent sheet into thetransparent sheet.
 12. An apparatus as defined in claim 11 wherein atleast either one of two surfaces of the transparent sheet is formed as alight diffusing surface.
 13. An apparatus as defined in claim 11 whereinthe transparent sheet contains light diffusing particles dispersedtherein.
 14. An apparatus as defined in claim 11, 12, or 13 wherein thestimulable phosphor sheet comprises a sheet-shaped transparent substrateand a stimulable phosphor layer overlaid on the sheet-shaped transparentsubstrate, and the transparent sheet of the sheet-shaped erasing lightsource acts also as the sheet-shaped transparent substrate of thestimulable phosphor sheet.
 15. An apparatus as defined in claim 9, 10,11, 12, or 13 wherein the stimulable phosphor sheet is kept stationaryat the position for image recording, and the image read-out meanscomprises: a) a read-out unit for irradiating the stimulating rays tothe stimulable phosphor sheet in a one-dimensional direction along amain scanning direction and detecting the light, which is emitted by thestimulable phosphor sheet when the stimulating rays are irradiated tothe stimulable phosphor sheet in the one-dimensional direction, and b)unit moving means for moving the read-out unit in a sub-scanningdirection.
 16. An apparatus as defined in claim 15 wherein the read-outunit comprises a linear stimulating ray source, which linearlyirradiates the stimulating rays to an area of the stimulable phosphorsheet, and a line sensor, which is located along the linear area of thestimulable phosphor sheet exposed to the linear stimulating rays andphotoelectrically detects the light emitted by the stimulable phosphorsheet when the stimulating rays are irradiated to the stimulablephosphor sheet.